JPH02246777A - Inverter - Google Patents

Abstract

PURPOSE:To ensure safety by detecting the voltage across a voltage detecting capacitor as a drive voltage to be applied onto an inverter unit body. CONSTITUTION:Energy is fed from a pulsating power source comprising an AC power source 1, a rectifying element 2 and a smoothing capacitor 7 to an inverter unit 13 which converts the energy into high frequency por to be fed to a load 4. A voltage detecting circuit 5 for detecting the voltage across a voltage detecting capacitor 9 to be charged through a diode 8 with driving voltage applied onto the inverter unit 3, and a control circuit 6 for increasing/ decreasing power supply to the load 4 based on the output from the voltage detecting circuit 5 and carrying out feed forward control are further provided.

Description

[Detailed description of the invention] [Industrial application field] The present invention is applied to an inverter device.

[Traditional techniques]

FIG. 7 shows a circuit diagram of a conventional inverter device.

The inverter device shown in FIG. 7 converts the voltage of an AC power source 1 such as a commercial power source into a pulsating current using a rectifying element 2, and further smoothes the current voltage using a smoothing capacitor 7. And AC i
Energy is supplied to the inverter main body 3 from a pulse iii source consisting of i R1, a rectifying element 2, and a smoothing capacitor 7. The inverter device main body 3 converts the given energy into high-frequency power and supplies it to a load 4 such as a high-pressure discharge lamp.

In such an inverter device, AC til! 1 fluctuates (increases or decreases), the output of the inverter main body 3 also fluctuates according to the fluctuation, making it impossible to stably supply high-frequency power to the load 4. In order to supply the voltage, it is necessary to detect the voltage applied to the inverter main body 3 in some way and control the output of the inverter main body 3 accordingly.

Therefore, in the circuit shown in FIG. 7, the collector and base of the NPN transistor 1) are connected to point a on the high voltage side of the smoothing capacitor 7 via the current limiting resistor 10, and the emitter of the transistor 1) is smoothed. It is connected to point b on the low voltage side of the capacitor 7. and an NPN transistor 12 that forms a current mirror with the transistor 1).
The base and emitter of transistor 1) are commonly connected to the base and emitter of transistor 1), respectively, and
is connected to a control circuit 6 between its collector and emitter.

The control circuit 6 changes the control signal given to the inverter main body 3 according to the magnitude of the impedance between the collector and emitter of the transistor 12.

Next, the operation of this inverter device will be explained.

When the ii [ii pressure of AC power supply 1 decreases, points a and b
The voltage between the points drops and passes through the resistor 1o to the transistor 1.
) decreases. Therefore, the impedance between the collector and emitter of transistor 12 increases. As a result, the control circuit 6 gives the inverter device main body 3 a control signal that lowers the oscillation frequency, for example, and thereby increases the output of the inverter device main body 3, so that even if the voltage of AC tal falls, the load 4 Feedforward control is performed so that the power supplied to the system does not decrease.

On the contrary, when the voltage of the AC power source 1 increases, the voltage between points a and b increases, and the output of the inverter main body 3 decreases in exactly the opposite operation to the above, causing the AC power source 1 to
Feedforward control is performed so that the power supplied to the load 4 does not increase even if the voltage increases.

As described above, the inverter device shown in FIG. 7 controls the power supplied to the load 4 to be constant regardless of voltage fluctuations of the AC it source 1.

[Problem to be solved by the invention]

However, in the inverter device shown in FIG. 7, the voltage across the smoothing capacitor 70, that is, at point a and
The voltage between the points has a waveform including a ripple component V, as shown by the solid line in FIG.

As a result, the control signal given from the control circuit 6 to the inverter main body 3 also fluctuates in accordance with the ripple component V, and the output of the inverter main body 3 also fluctuates in the same way, causing the power given to the load 4 to become unstable. There was a problem. Note that the broken line in FIG. 8 indicates a full-wave rectified waveform of the voltage of the AC source 1.

In addition, a slight abnormality occurs in the voltage of AC voltage 'a1,
When an instantaneous power outage or an instantaneous voltage drop occurs, the voltage between points a and b may drop more than the range of variation expected when the source voltage is normal.

In such a case, too much feedforward is applied from the control circuit 6 to the inverter main body 3, and as a result, too much current flows from the inverter main body 3 to the load 4, causing an abnormality in the inverter main body 3, and in some cases, There was a risk that the inverter main body 3 would be destroyed.

In order to solve this problem, the capacitance CI of the smoothing capacitor 7 connected to the output side of the rectifying element 2 can be made extremely large to suppress the ripple component V shown in FIG. It is also possible to prevent the voltage between points a and b from dropping too much even if a power outage or instantaneous voltage drop occurs.

However, if the capacitance IC of the smoothing capacitor 7 is set too large, the voltage between points a and b will fall slowly when the power is cut off, and the output of the inverter main body 3 will remain at ma for a while even after the power is cut off. However, there are safety issues. Further, there is a problem in that the use of a large capacity smoothing capacitor 7 increases the cost.

It is an object of the present invention to reduce the influence of ripple components remaining in the power supply voltage, to prevent abnormalities and destruction of the inverter device body caused by power supply abnormalities, and to reduce the voltage at the time of power interruption. An object of the present invention is to provide an inverter device that can ensure safety by speeding up the fall of the voltage.

[Means to solve the problem]

The inverter device according to claim (1) detects the voltage across the voltage detection capacitor charged via the unidirectional element with the drive voltage applied to the inverter device body as the drive voltage applied to the inverter device body. By providing a voltage detection circuit and increasing or decreasing the power supplied from the inverter device to the load according to the output of this voltage detection circuit, the power supplied to the load can be kept constant regardless of fluctuations in the drive voltage applied to the inverter device. A control circuit is provided for feedforward control.

The inverter device of claim (2) is an inverter device in which a smoothing capacitor is provided at the output end of a rectifying element, in which the smoothing capacitor has a capacity of 01, the voltage detection capacitor has a capacity of 02, and the smoothing capacitor has a capacity of 02. When the equivalent impedance of the inverter device and the load as seen is 21, and the equivalent impedance of the voltage detection circuit other than the voltage detection capacitor and the control circuit as seen from the voltage detection capacitor is 22, Z
,・C1/Z2・C2<1.

In the inverter device of claim (3), the circuits other than the voltage detection capacitor of the voltage detection circuit have a current mirror configuration.

[For production]

According to the structure of claim (1), the voltage detection circuit applies the voltage across the voltage detection capacitor charged via the unidirectional element with the driving voltage applied to the inverter main body to the inverter main body. Since the drive voltage is detected as a driving voltage, the unidirectional element prevents the discharge of NN from the voltage detection capacitor to the inverter main body. As a result, even if there is a ripple in the output voltage of the rectifying element, fluctuations in the voltage across the voltage detection capacitor due to the ripple can be suppressed to a small level. Therefore, the influence of ripples in the output voltage of the rectifying element on the control signal output from the control circuit is also reduced.

Furthermore, the effect of ripple on the output voltage of the rectifier is reduced on the output voltage of the inverter, and high-frequency power is stably transmitted from the inverter to the load regardless of the presence or absence of a smoothing capacitor on the output side of the rectifier. can be supplied.

The inverter device according to claim (2) includes a lever, Zl.C1/
By setting Z2·C2<1, it is possible to sufficiently reduce the influence of ripple on the output voltage of the rectifying element in the voltage detection capacitor.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an inverter device according to a first embodiment of the present invention. This inverter device converts the voltage of an AC power source 1 such as a commercial power source into a pulsating current using a rectifying element 2, and further converts the voltage of an AC power source 1, such as a commercial power source, into a pulsating current using a smoothing capacitor 7. ! Smooth the pressure.

And AC power supply 1. Energy is supplied to the inverter main body 3 from a pulsating current source consisting of the rectifying element 2 and the smoothing capacitor 7. The inverter main body 3 converts the applied energy into high-frequency power and supplies it to a load 4 such as a high-pressure discharge lamp.

Further, in this inverter device, a voltage across a voltage detection capacitor 9 that is charged via a unidirectional element 8 made of, for example, a diode with a driving voltage applied to the inverter device main body 3 is applied to the inverter device main body 3. A voltage detection circuit 5 is provided to detect the drive voltage, and the drive voltage applied to the inverter main body 3 is increased or decreased by increasing or decreasing the power supplied from the inverter main body 3 to the load 4 according to the output of the voltage detection circuit 5. The control circuit 6 includes a control circuit 6 that performs feedforward control to keep the power supplied to the load 4 constant regardless of fluctuations.

In this case, the voltage detection circuit 5 connects one end of the voltage detection capacitor 9 to point a on the high voltage side of the smoothing capacitor 7 via the unidirectional element 8, and connects the other end of the voltage detection capacitor 9 to the point a on the high voltage side of the smoothing capacitor 7. It is connected to point b on the low voltage side of capacitor 7.

In addition, the collector and base of an NPN transistor 1) are connected to one end of the voltage detection capacitor 9 via a current limiting resistor 10, and the emitter of the transistor 1) is connected to the other end of the voltage detection capacitor 9, that is, a smoothing transistor 1). It is connected to point b on the low voltage side of the capacitor 7. The base and emitter of an NPN transistor 12 that forms a current mirror with the transistor 1) are commonly connected to the base and emitter of the transistor 1), respectively, and the collector and emitter of the transistor 12 are connected to the control circuit 6. are doing. The control circuit 6 changes the control signal given to the inverter main body 3 according to the magnitude of the impedance between the collector and emitter of the transistor 12.

Next, the operation of this inverter device will be explained.

When the power supply voltage of the AC power supply 1 decreases, the voltage between points a and b decreases, and the voltage across the voltage detection capacitor 9 also decreases. As a result, transistor 1 is connected through resistor 10.
) decreases.

Therefore, the impedance between the collector and emitter of transistor 12 increases. As a result, the control circuit 6 gives a control signal to the inverter main body 3 to lower the oscillation frequency, thereby increasing the output of the inverter main body 3, so that even if the voltage of the AC power supply 1 drops, the load 4 Feedforward control is performed so that the power supplied to the system does not decrease.

Conversely, when the voltage of the AC power supply 1 increases, the voltage between points a and b increases, and the voltage across the voltage detection capacitor 9 also decreases. As a result, the output of the inverter main body 3 is reduced in an operation exactly opposite to the above, and feedforward control is performed so that the power supplied to the load 4 does not increase even if the voltage of the AC power supply 1 increases.

As described above, the inverter device shown in FIG. 1 controls the power supplied to the negative r@4 to be constant regardless of voltage fluctuations of the AC power supply 1.

Here, in the above-described operation, the influence of voltage ripple between point a and point b will be considered.

The magnitude of the ripple of the smoothing capacitor 7 is determined by assuming that the capacitance of the smoothing capacitor 7 is C0, and that the equivalent impedance of the inverter main body 3 and load 4 seen from the smoothing capacitor 7 is 21, as shown in the second diagram. Sometimes C,X
It is proportional to Z. Furthermore, the magnitude of the ripple of the voltage detection capacitor 9 is determined by the capacitance of the voltage detection capacitor 9 being 02
The voltage detection circuit 5 seen from the voltage detection capacitor 9
Circuits other than the voltage detection capacitor 9 and the control circuit 6
When the equivalent impedance of is 22, C2X22
is proportional to.

The equivalent impedance Z1 is the voltage ■1 applied to the equivalent impedance Z1 in the second time and the equivalent impedance Z
From the current flowing into 1), Zl=V]/T.

It is expressed as Further, the equivalent impedance Z2 is similarly expressed as Z2=v2/1□ from the applied voltage V2 to the equivalent impedance Z2 and the ii current I 2 flowing into the equivalent impedance Z2.

In this case, the equivalent impedance Z1 is determined by the inverter main body 3 and the load 4. Further, the equivalent impedance Z2 is determined by the feedforward signal to the control circuit 6, and in the case of FIG. 2, it is approximately determined by the resistance value R of the resistor 10. Therefore, the equivalent impedance 2. ．．
22 is in the relationship Z 1 × Z 2 .

Now, smoothing capacitor 7 and voltage detection capacitor 9
The capacity tc, , C2 and the equivalent impedance 2, . 22 is set in the relationship of (Z, The influence of the ripple of the voltage across the voltage detection capacitor 7 hardly appears on the voltage across the voltage detection capacitor 9, and the power supplied to the load 4 can be stabilized.

In addition, by setting the value of z2x02 to a large value, it is possible to suppress the drop in voltage across the voltage detection capacitor C2 to a small value when a momentary power outage or instantaneous voltage drop occurs for a short period of time. When a momentary power outage or a momentary voltage drop occurs, it is possible to prevent excessive feed forward from the control circuit 6 to the inverter main body 3. Therefore, occurrence of abnormality or destruction of the inverter device main body 3 can be prevented.

In addition, by setting the values of z and xCl small, the charge of the smoothing capacitor 7 is quickly discharged when the AC power supply 1 is cut off, and the operation of the inverter device main body 30 continues for a long time after the AC power supply B1 is cut off. Safety can be ensured without having to do so.

FIG. 3 shows a more specific circuit diagram of the inverter device shown in FIG. 1. In FIG. 3, the inverter main body 3 is
It consists of a series circuit of transistors 13 and 14 connected between both ends of the smoothing capacitor 7, and a series circuit of a resonance choke coil 15 and a resonance capacitor 16, one end of which is connected to the midpoint of the transistor 13 and 14. A load 4 is connected between both ends of the transistor 14 via a series circuit including a resonant choke coil 15 and a resonant capacitor 16.

The control circuit 6 includes an oscillator 17, a level shift transformer 20, and resistors 18 and 19. resistance 1
8. The series circuit of 19 has a common power supply voltage V with the oscillator 17.
cc, and their midpoint is connected to the control voltage input terminal C of the oscillator 170.

The oscillator 17 changes its oscillation frequency according to the voltage level applied to the control voltage input terminal C.

In this case, when the voltage applied to the control voltage input terminal C becomes high, square wave signals having a low frequency and mutually inverted phases are output from the output terminals d and e, and from the output terminal d, the signals are outputted from the transistor 13 via the transformer 20. from the output terminal e directly to the gate of the transistor 14.

On the other hand, when the voltage applied to the control voltage input terminal C becomes low, square wave signals with a high frequency and mutually inverted phases are output from the output terminals d and e, and similarly, the transistor 1
3. Added to gate 14. As a result, the two transistors 13.1 constituting the inverter main body 3
4 are turned on alternately, and power is supplied to the load 4 from the midpoint of the transistors 13 and 14 via the series circuit of the resonant choke coil 15 and the resonant capacitor 16.

The resistor 19 includes a transistor 12 of the voltage detection circuit 5.
The collector and emitter of the transistor E2 are connected in parallel, and the oscillator 1 responds to changes in the impedance of the transistor E2.
70 The voltage applied to the control voltage input terminal C changes.

In this case, when the voltage across the smoothing capacitor 7, that is, the voltage between points a and b increases, the impedance of the transistor 12 of the voltage detection circuit 5 decreases as described above, and the control voltage input terminal of the oscillator 17 The voltage at C decreases. As a result, the frequency of the square wave signal output from the output terminals d and e of the oscillator 17 becomes high (and the power supplied to the load 4 decreases).

Further, when the voltage between points a and b decreases, the impedance of the transistor 12 of the voltage detection circuit 5 increases as described above, and the voltage of the control voltage input terminal C of the oscillator 17 increases. As a result, the frequency of the square wave signal output from the output terminals d and e of the oscillator 17 becomes lower, and the power supplied to the load 4 increases.

Points other than the above are as explained in connection with FIG.

As described above, according to the inverter device of this embodiment, compared to the conventional example, the power supplied to the load 4 is stabilized,
Even if a momentary power outage or a momentary voltage drop occurs in the AC power supply 1, the inverter main body 3 can be operated without abnormality. Furthermore, there is no need to increase the capacity of the smoothing capacitor 7, and there is no need for the newly added voltage detection capacitor 9 to have a large capacity, so the cost does not increase.

FIG. 4 shows a circuit diagram of an inverter device according to a second embodiment of the present invention. In the inverter device shown in FIG. ' by changing the impedance value of the variable impedance element 27 inserted between the inverter main body 3' and the load 4 instead of changing the output of the inverter main body 3'. The power supplied to tJ4 is stabilized.

This will be explained in more detail below.

Similar to the embodiment shown in FIG. 1, this inverter device converts the voltage between both ends of the smoothing capacitor 7 into
In addition to this, high frequency power is supplied from the inverter main body 3' to the load 4 via the variable impedance element 27. The inverter main body 3' is composed of an oscillation transformer 23, two transistors 24 and 25, and a resonant capacitor 26, and oscillates at a constant frequency determined by circuit constants. 21 is a transformer, and 22 is a base circuit for transistors 24 and 25.

The configurations of the unidirectional element 8 and the voltage detection circuit 5 are similar to those in the embodiment shown in FIG. 1, and the impedance value of the transistor 12 changes in response to changes in the voltage across the smoothing capacitor 70. The control circuit 6' then controls the transistor 1
By controlling the impedance value of the variable impedance element 27 according to the change in the impedance value of the variable impedance element 27,
As in the first embodiment, the power supplied to the load 4 is stabilized regardless of fluctuations in the voltage across the smoothing capacitor 7.

Points other than the above are the same as those in the first embodiment, and detailed explanation will be omitted.

The effects of this embodiment are similar to those of the first embodiment.

FIG. 5 shows a circuit diagram of an inverter device according to a third embodiment of the present invention. The inverter device in FIG. 5 uses a voltage detection circuit 5' in place of the voltage detection circuit 5 in FIG. The other configurations are the same as those shown in FIG.

This voltage detection circuit 5' does not use a current mirror configuration to change the impedance of the transistor 12 as in the circuit shown in FIG. By applying this voltage as a base bias voltage between the base and emitter of the transistor 32, the impedance between the collector and emitter of the transistor 32 is changed.

The effects of this embodiment are similar to those of the first embodiment.

FIG. 6 shows a circuit diagram of an inverter device according to a fourth embodiment of the present invention. The inverter device of FIG. 6 uses a voltage detection circuit 5# in place of the voltage detection circuit 5' of FIG. 5, and the other configuration is the same as that of FIG. 1.

This voltage detection circuit 5'' does not directly divide the voltage of the voltage detection capacitor 9 with a resistor 10.31 as shown in FIG.
A series circuit of resistor 3 and resistor 34 is provided in parallel, and the voltage of resistor 34 is divided by resistor 10.31.

With this configuration, the detection voltage V of the voltage detection capacitor 9. Rather than the control action being performed on 2, (
Control operation will be performed for Vo2-E),
Voltage V of voltage detection capacitor 9. 2 is lower than voltage E, no control action is performed.

In addition, the above DC! #33 can be realized, for example, by a circuit that rectifies a part of the high-frequency output of the inverter device main body 3 using a rectifier (not shown), and further smooths it with a capacitor (not shown) via a resistor.

The inverter main body 3 shown in the embodiment shown in FIG. 3 is a half-bridge type, and the embodiment shown in FIG. 4 is an L-push-pull type, but other types of inverter It goes without saying that the present invention can be applied to, for example, a single-stone inverter and other types of inverter devices.

In addition, as a control method for the output of the inverter main body 3,
In the above embodiment, the output was controlled by changing the oscillation frequency, but in addition to this, the inverter can also be controlled by a so-called pulse width control method that changes the duty ratio of the drive signal applied to the switching elements constituting the inverter main body 3. The output of the device main body 3 may be controlled, and any specific means for controlling the output of the inverter device main body 3 may be used.

Further, in the above embodiment, an inverter device having a smoothing capacitor 7 has been described, but the present invention is also effective for an inverter device not having a smoothing capacitor.

〔Effect of the invention〕

According to the inverter device of claim (1), the voltage detection circuit applies the voltage across the voltage detection capacitor charged via the unidirectional element with the drive voltage applied to the inverter device main body to the inverter device main body. Since the configuration detects the drive voltage as the driving voltage, even if the capacitance of the smoothing capacitor on the output side of the rectifying element is small or absent, it is possible to reduce the influence of ripple components remaining in the source voltage. It is possible to prevent the occurrence of abnormalities and destruction of the inverter device body due to abnormalities, and it is also possible to ensure safety by quickly dropping the voltage when the power is cut off, and it is also inexpensive in terms of cost. .

According to the inverter device of claim (2), Zl.C1/
By setting Z2·C2<1, it is possible to sufficiently reduce the influence of ripples on the output voltage of the rectifying element in the voltage detection capacitor.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an inverter device according to a first embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of the circuit in FIG. 1,
3 is a circuit diagram embodying the circuit of FIG. 1, FIG. 4 is a circuit diagram showing the configuration of an inverter device according to a second embodiment of the invention, and FIG. 5 is a circuit diagram of a third embodiment of the invention. 6 is a circuit diagram showing the configuration of an inverter device according to a fourth embodiment of the present invention, FIG. 7 is a circuit diagram showing an example of a conventional inverter device, and FIG. is a waveform diagram of the voltage applied to the inverter device main body. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Rectifying element, 3... Inverter device main body, 4... Load, 5... Voltage detection circuit,
6... Control circuit, 7... Smoothing capacitor, 8...
・Unidirectional element, 9... Voltage detection capacitor 1-- Alternating υ, 2-- Rectifying element 5- On the other hand, in the season, rare ÷ 9-- is 5゜

Claims (3)

[Claims] (1) An inverter device body that supplies high-frequency power to a load, a rectifying element that rectifies the voltage of an AC power source and applies it to the inverter device body, and a unidirectional element using a drive voltage applied to the inverter device body. a voltage detection circuit that detects a voltage across a voltage detection capacitor charged through the inverter as a drive voltage applied to the inverter main body;
By increasing or decreasing the power supplied from the inverter device main body to the load according to the output of this voltage detection circuit, the power supplied to the load is constantly fed regardless of fluctuations in the drive voltage applied to the inverter device main body. An inverter device equipped with a control circuit that performs forward control. (2) In an inverter device in which a smoothing capacitor is provided at the output end of the rectifying element, the capacitance of the smoothing capacitor is C_1, the capacitance of the voltage detection capacitor is C_2, and the When the equivalent impedance of the inverter main body and the load is Z_1, and the equivalent impedance of the circuit other than the voltage detection capacitor of the voltage detection circuit and the control circuit as seen from the voltage detection capacitor is Z_2, (Z_1× C_1)/(Z_2×C_2)<1
Claim (1) characterized in that it is set to satisfy the following:
The inverter device described. (3) Claim (1) wherein circuits other than the voltage detection capacitor of the voltage detection circuit have a current mirror configuration.
Or the inverter device described in (2).